Date of Award

Fall 12-15-2017

Level of Access

Campus-Only Thesis

Degree Name

Master of Science (MS)

Department

Civil Engineering

Advisor

Eric Landis

Second Committee Member

Edwin Nagy

Third Committee Member

Roberto Lopez-Anido

Abstract

Fracture of fiber reinforced ultra-high performance concrete mobilizes several different energy dissipation mechanisms. For most practical applications, the two dominant mechanisms are the fracture of the concrete matrix, and the debonding and pullout of the embedded fibers. While the overall energy dissipation is a simple measurement, the relative contribution of the different mechanisms is not. In this work, acoustic emission signals generated during split cylinder, three point bending notched beam and fiber pull out tests were recorded and analyzed by different signal processing techniques to establish a universal approach for acoustic emission source classification. As a part of this work, fiber orientation analysis was evaluated on cylinder specimens in order to quantify effect of the fiber inclination angle on the amount of work done by fracture during the test. An optimum and pessimum orientation was established based on the orientation of the fibers relative to the axes of principal stress. Test results confirmed assumptions made for fiber orientation analysis, in that specimens oriented in optimum position showed higher load peaks and work of load comparing to specimens oriented in pessimum position. For acoustic emission analysis, a combination of unsupervised and supervised learning algorithms for neural network training were used in this work and showed to be effective tool for acoustic emission data classification problem. Cross correlation, wavelet decomposition and frequency domain analysis were performed and resulted to be useful but limited tools as preliminary data analysis.

The acoustic emission analysis showed that most of energy is dissipated through fiber pullout mechanism for specimens oriented in optimum and arbitrary position, while matrix cracking is dominant for pessimum oriented specimens.

Comments

Fracture of fiber reinforced ultra-high performance concrete mobilizes several different energy dissipation mechanisms. For most practical applications, the two dominant mechanisms are the fracture of the concrete matrix, and the debonding and pullout of the embedded fibers. While the overall energy dissipa- tion is a simple measurement, the relative contribution of the different mechanisms is not. In this work, acoustic emission signals generated during split cylinder, three point bending notched beam and fiber pull out tests were recorded and analyzed by different signal processing techniques to establish a universal approach for acoustic emission source classification. As a part of this work, fiber orientation analysis was evaluated on cylinder specimens in order to quantify effect of the fiber inclination angle on the amount of work done by fracture during the test. An optimum and pessimum orientation was established based on the orientation of the fibers relative to the axes of principal stress. Test results confirmed assumptions made for fiber orientation analysis, in that specimens oriented in optimum position showed higher load peaks and work of load comparing to specimens oriented in pessimum position. For acoustic emission analysis, a combination of unsupervised and supervised learning algorithms for neural network training were used in this work and showed to be effective tool for acoustic emission data classification problem. Cross correlation, wavelet decomposition and frequency domain analysis were performed and resulted to be useful but limited tools as preliminary data analysis. The acoustic emission analysis showed that most of energy is dissipated through fiber pullout mechanism for specimens oriented in optimum and arbitrary position, while matrix cracking is dominant for pessimum oriented specimens.

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